1. Technical Fields
The present invention relates to a technique for mounting a conductive wire to teeth of a resolver.
2. Background of the Related Art
A resolver is used for high-accuracy detection of a rotational position of a rotor magnet in a brushless motor. The resolver includes a resolver stator having a plurality of teeth formed on an inner circumference thereof, and a resolver rotor rotatably arranged in the resolver stator. The resolver rotor is mounted coaxially with the rotor magnet in the brushless motor so as to rotate integrally with the rotor magnet.
A conductive wire is wound around each of the teeth of the resolver stator to form an excitation winding or an output winding. Variation in voltage output from the output winding is detected in accordance with variation in radial distance between an inner circumferential face of the teeth of the resolver stator and an outer circumferential face of the resolver rotor, thereby the rotational position of the rotor magnet in the brushless motor is detected.
The excitation winding or the output winding formed around each of the teeth is connected to a plurality of terminal pins provided on a terminal block attached radially outward from the teeth of the resolver stator. The terminal block is generally made of a resin member. Therefore, it is required to consider that the terminal block is expandable when heat is applied thereto. That is, in a case where the conductive wire has no slack in a portion connecting the teeth and the terminal pin, the conductive wire in the portion connecting the teeth and the terminal pin may be excessively strained due to thermal expansion of the terminal block. As a result, the conductive wire in the portion connecting the teeth and the terminal pin is possibly cut off.
In a case where the brushless motor is used in an environment (e.g., in an automobile) easily affected by heat thermal expansion of a member thereof needs to be taken into consideration.
Therefore, arrangements are conventionally made such as providing sufficient slack to the conductive wire in the portion connecting the teeth and the terminal pin.
According to a first structure of a conventional resolver, a longitudinal bar member is arranged between the teeth and the terminal pin when a winding machine connects the teeth and the terminal pin with the conductive wire. The conductive wire is connected to the terminal pin while in contact with a top face of the longitudinal bar member which is removed in a direction substantially perpendicular to a direction of the conductive wire crossing the longitudinal bar member after the conductive wire is connected. Accordingly, the conductive wire thus connected is provided with slack.
According to a second structure of the conventional resolver, the terminal block is provided with a through-hole so that a plate shaped fitting is inserted between the teeth and the terminal pin from a back of the terminal block. In such a structure, the conductive wire is connected to the terminal pin while in contact with a top face of the fitting projecting upward from a top face of the terminal block. The fitting is taken downward out of the terminal block after the conductive wire is connected to the terminal pin. Accordingly, the conductive wire thus connected is provided with slack.
According to a third structure of the conventional resolver, there are arranged between the teeth and the terminal pin a plurality of slackening pins for slackening the conductive wire. The slackening pins are respectively inserted into a plurality of holes provided in the terminal block from the back of the terminal block to be arranged so as to project from the top face of the terminal block in a substantially vertical direction thereto. The conductive wire is connected to the terminal pin while in contact with a side face of the slackening pin. After the conductive wire is connected, the slackening pin is taken downward out of the terminal block. Accordingly, the conductive wire thus connected is provided with slack.
As described above, various arrangements have been made to provide slack to the conductive wire between the teeth and the terminal pin in the resolver. However, in the first conventional structure, there is a problem that the conductive wire is damaged as the longitudinal bar member is laterally pulled out while the conductive wire contacts the top face of the longitudinal bar member. In the second conventional structure, it is required to provide the terminal block with a large space for inserting the fitting, resulting in deteriorated intensity of the terminal block. Further, in the first and second conventional structures, since the conductive wire is pushed upward to have slack, there is another problem that the conductive wire is difficult to be wound around the respective teeth with the winding machine due to force of pulling the conductive wire upward.
In the third conventional structure, the slackening pins are taken out downward while in contact with the conductive wire, causing the problem that the conductive wire is damaged.